Opponents of a new Michigan bill that would offer parents tax credits for unborn fetuses say the legislation is an attempt to implement "personhood" ideology into law. Photo: Reuters

Mississippi voters rejected an amendment to the state constitution that would have declared life begins at conception, a controversial proposal that would have outlawed abortion as well as several forms of birth control if passed.

The Personhood Amendment, officially known as Initiative 26, was rejected by 58 percent of voters, a setback for abortion opponents who hoped to use its passage as a stepping stone to overturn the Supreme Court decision legalizing abortion in the U.S..

The amendment would have given fertilized human eggs legal rights by defining a person as every human being, from the moment of fertilization, cloning or the functional equivalent thereof. The amendment would have outlawed abortion, even in cases of rape or incest, and may have criminalized physicians who performed those procedures on women experiencing life-threatening pregnancies.

By extension, the law could have gone as far as banning in-vitro fertilization as well as birth control methods such as the morning-after pill or intrauterine devices.

Several pro-choice groups have hailed the failure of Initiative 26 as massive victory for women's reproductive and constitutional rights.

Today's vote is a huge victory for anyone concerned about protecting our constitutional rights against erosion. And it sends an unequivocal message to proponents of these measures -- that the American people, no matter the political perspective, will not stand for such blatant attacks on the health and constitutionally protected rights of women in this country, said Nancy Northup, the president and CEO of the Center for Reproductive Rights.

Felicia Brown-Williams of the Mississippi Healthy Families Campaign told CNN that while Mississippi is a fairly conservative state, its voters were able to recognize the threats posed by Initiative 26.

I think voters rejected a measure they understood to be dangerous, said Brown-Williams. They really tried to manipulate values around faith and family.

The proposal was pushed by Personhood USA, a Colorado-based group that has been driving similar legislative efforts for years. Voters in Colorado rejected similar ballot initiatives in 2008 and 2010.

However, Personhood supporters are ready to keep fighting. Keith Mason, the group's co-founder, told The Associated Press that he intends to renew efforts to pass Personhood legislation or ballot initiative in Mississippi. Personhood USA is also fighting to land similar initiatives on 2012 ballots in Florida, Montana, Ohio, Oregon, Nevada and California.

We accomplished our mission to be a voice for the voiceless who have no one else speaking for them, said Mason. I want to make a commitment that we will stand with Mississippi until all humans are treated as persons.